1. Field of the Invention
The present invention relates to a method and apparatus for driving roller shutter doors to a closed or open state. More specifically, the present invention relates to a controller for applying motive power to a roller shutter door of the type used to retard passage in the event of fire, smoke or similar conditions, or, of doors simply used to prevent egress or entrance based on the time of day or the opening or closing of the facility to which the door is a portal.
2. Description of the Related Art
Roller shutter doors have been known for some time and are used in a variety of applications. They include such categories as: rolling grille; storm doors; fire and smoke doors; air-leakage doors, counter shutters; and, the like. What they have in common is a construction that allows them to be rolled up onto a drum or tube when in the open position; or, to be unreeled from the drum when the door is being lowered. Theses doors are typically used in commercial establishments to seal or close off large doorways, or bays, and can be operated electrically, manually, or both.
The methods and systems for driving the doors into an upward or downward position, during normal or emergency operation, have evolved over time from simple pull down doors of a kind used in residential garages, to more technologically advanced electric drive systems with timers, manual over-rides, and diverse safety features.
Generally, commercial or large capacity fire doors were driven by electric motors to open or close the door. However, when a fire occurred, these mechanisms would disengage the motor from the fire door and allow the door to close under the pressure exerted by an auxiliary spring activated by mechanical means or from a counterbalance. These mechanical means included pendulums, oscillating governors, friction discs, ratchets, etc. These mechanical devices tended to be unreliable because of jamming or other malfunctions caused by the motion of the door. One early mechanism that attempted to address this problem was described in U.S. Pat. No. 5,203,392 for a Mechanism For Controlling The Raising And Lowering Of A Door, issued Apr. 20, 1993 to Shea (hereinafter referred to as “Shea”).
In Shea, there is disclosed a mechanism for controlling the opening and closing of a door such as a fire door. The mechanism controls the speed of the door when it drops under the force of gravity; and, can be electrically, or manually, operated. The problem that Shea was attempting to address was the need for a fire door mechanism that regulates the raising and lowering of the door while effectively controlling the door's movement without the need of springs or similar mechanical means. The speed of the door's drop was under control of a centrifugal governor employing brake shoes.
Other prior art has addressed the need for testing the speed and effects of the door's drop during non-emergency uses. U.S. Pat. No. 5,482,103 for a Door Apparatus With Release Assembly, issued Jan. 9, 1996 to Burgess et al. (hereinafter referred to as “Burgess”) teaches the use of a counterweight to offset the weight of the roller door and a reducing weight to reduce the weight of the counterweight. The assembly of the door allows the use of a standard governor to control downward speed. This use of reduced weight and the resultant reduced stress on the door allows the mechanism to use parts that are reduced in size and weight.
After the disclosures of Shea and Burgess, came the teachings of U.S. Pat. No. 5,924,949 for an Apparatus For Driving A Roller Shutter Door, issued Jul. 20, 1999 to Fan (hereinafter referred to as “Fan”). Fan teaches a driving mechanism for roller shutter doors that can be adjusted from outside of the apparatus so as to accommodate doors of different heights. The advantage of Fan is that the mechanism, if either moved from a door of one height to a door of a differing height, or if the door is not of the height for which the factory settings apply, does not have to be disassembled for adjustments. Rather, the adjustable control means is disposed within the stationary housing of the apparatus, and extends from within the apparatus to a point outside where it can be manipulated or adjusted as required. And, while Fan addresses a legitimate need, it still leaves unanswered the need to allow the door to move freely into an open position while under control of a governor.
Further improvements to the drive mechanism are taught in U.S. Pat. No. 6,530,863 for a Door Operator Unit, issued Mar. 11, 2003 to Balli et al. (hereinafter referred to as “Balli”). In Balli, an improved power transmission mechanism which works between the drive motor and the operator output shaft is disclosed. The operator unit is adapted to reverse the positions of a manual operator drive and a release mechanism. The advantage provided by Balli is the ability to interchange the operator unit components depending upon the door configuration or application. Thus, the drive mechanism can be established as either a right side or a left side mount. Balli still leaves the question of door control after rebounding, or the issue of timer adjusted openings and closings to be addressed.
The evolution of the rollup door and its drivers and safety mechanisms has continued with the disclosures of U.S. Pat. No. 7,261,139 for a Manual Operating Mechanism For Upward Acting Door, issued Aug. 28, 2007 to Varley et al. Varley teaches a mechanism that addresses the difficulty of operating a roll-up door manually in those cases where the drive motor is mounted in an assembly that is beyond the easy reach of the user. The mechanism of Varley includes a manual brake release that is foot actuated by a person using an elongated crank handle to manually move the door from an open to closed position or vice versa. A problem left unanswered by Varley is how an operator, under the stress of an emergency, can efficiently disengage the motor drive.
What is not appreciated by the prior art is the need to provide a method and apparatus for controlling the drop of the door (or curtain as the case may be) that incorporates each of the successes of the prior art while minimizing the problems. One important issue not addressed by the prior art, is that the drop of the door should be controlled by a mechanical centrifugal governor such that the door does not “bounce” after it arrives in the full open position. While in a closed position, the curtain or door must be able to maintain its locked position unless the door or curtain is manually released through the use of a manual lever and/or an electrical switch. The use of a timer to allow the door to re-open at least part-way, and then close after a specific time interval during an emergency, would provide a safety that is currently lacking in the art.
Accordingly, there is a need for an improved method and apparatus that will supply multiple safety features in the event of an emergency while providing for more efficient operation of the door during normal use.